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Solutions

Solutions. Solute + Solvent. Bell work 4/20. What happens to something when it dissolves?. Agenda. Solution stations – debrief Notes Molarity problems practice HW: molarity problems; practice quiz Wednesday: Quiz (molarity; redox). Solute. The compound being dissolved

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Solutions

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  1. Solutions Solute + Solvent

  2. Bell work 4/20 • What happens to something when it dissolves?

  3. Agenda • Solution stations – debrief • Notes • Molarity problems practice • HW: molarity problems; practice quiz • Wednesday: Quiz (molarity; redox)

  4. Solute The compound being dissolved Usually the compound in the smaller amount Can be solids, liquids, or gases Lab: salt & sugar

  5. Solvent The compound or molecule doing the dissolving Usually the compound in the LARGER amount Can be solids, liquids, gases Lab: water & saliva

  6. Solution Animation of NaCl and Water Watch when the salt meets the water Is there room for more solute? Your solution is described as unsaturated Your solution is described as saturated What if I keep adding solute anyway? You will have a saturated solution with undissolved particles on the bottom.

  7. The Solution Spectrum Less Solute Maximum More solute than max. solute Unsaturated Saturated Supersaturated (extraordinary)

  8. A saturated solution Contains the MAXIMUM amount of solute for a given quantity of solvent at a constant temperature and pressure. Adding additional solute to a saturated solution will not dissolve

  9. A saturated solution is a state of dynamic equilibrium

  10. A supersaturated solution contains MORE solute than it can theoretically hold at a given temperature. An unsaturated solution contains LESS solute than a saturated solution at a constant temperature and pressure

  11. Solution Animation of AgBr and Water Watch when the salt meets the water • Is there room for more solute? Your solution is described as unsaturated Your solution is described as saturated What if I keep adding solute anyway? You will have a saturated solution with undissolved particles on the bottom.

  12. Which is more soluble in water? AgBr- Saturated solution (45) NaCl Saturated solution (185)

  13. And the winner is…. NaCl is MORE soluble in water than AgBr You can add more NaCl to water before it stops dissolving

  14. Solubility Is the amount of solute that can be dissolved in a solvent g of solute 100g of solvent Is a unique property of a compound Can be observed with our eyes-lab or simulations Can Google it-NaCl solubility in water 35.6 g/100 mL (0 °C)35.9 g/100 mL (25 °C)39.1 g/100 mL (100 °C) Read a solubility curve

  15. Solubility Curve super saturated saturated unsaturated

  16. Temperature = Collisions

  17. When the solute is….. Liquid or Solid: You can dissolve more solute-it becomes more soluble at higher temperatures Gas: You can dissolve less because the higher temperature allows the gas to escape- the collisions “bump” the gas out of solution.

  18. Practice Problem What mass of solute will dissolve in 100 g of water at the following temperatures? 1) Potassium Nitrate at 70°C  2) Sodium Chloride at 100°C  3) Ammonium Chloride at 90°C Which of the three substances is most soluble in water at 15°C?

  19. Describe a solution Using the terms saturated, unsaturated, or supersaturated, how would you describe 120g of Potassium Iodide in 100 g of water at 30C? 140g of Potassium Iodide in 100 g of water at 0C?

  20. How many grams of potassium chloride can be dissolved in 200g of water at 80°C? From the solubility curve we know The solubility of KCl at 80°C=50g KCl 100 g H2O 200 g H2O x 50g KCl = 100 g KCl 100 g H2O

  21. If a saturated solution of potassium chlorate is cooled from 80°C to 50°C, how many grams of precipitate is formed? • Find the solubility of KClO3 at 80°C= 40gKClO3/100g H2O 2) Find the solubility of KClO3 at 50°C= 20gKClO3/100g H2O 40g – 20 g = 20 g KClO3 would precipitate at 50°C

  22. If I have 60 ml of a saturated sodium nitrate solution at 10°C, how many grams of solute are in the solution? • Look at chart, use density of water 60 mL H2O x 1 g H2O x 80 g NaNO3 1 ml H2O 100 g H2O = 48 g NaNO3

  23. How would you make lemonade without directions?

  24. Lemonade is a Solution We increased the RATE of lemonade going into solution by Stirring it (agitation) Heating it Making smaller pieces All increased the number of collisions between the solute and solvent.

  25. Why didn’t we like our lemonade? Too sweet-concentrated, strong, lots of sweet particles What did we change? Added more water “science word”- Increased the VOLUME of the water No flavor-too weak, dilute, not enough sweet particles What did we change? Added more lemonade “science word”- Increased the MASS of the lemonade

  26. What math relationship describeshow a glass of lemonade tastes? Mass of lemonade Volume of Water Adding “science words” Mass of solute x Molar Mass = Moles of Solute Volume of solution Volume of solution

  27. Molarity Number of molesof solute dissolved in 1L of solution. Molarity (M) = moles of solute L of solution (L of solution=volume of solute + volume of solvent) Units: M (Ex. 0.5M)

  28. Molarity: Why does it matter? • Take a minute to think about why molarity matters. • Think of some examples of why it might be important to know the precise concentration of a solution • Brainstorm a list • Share your list with your table partner

  29. Sample Problems • Calculate the molarity for a solution whose volume is 1.2 L if it contains 0.020 moles of dissolved NaOH • What is the molarity of an aqueous solution containing 22.0 g of HCl in 1.5 L of solution?

  30. Sample Problems • Calculate the molarity for a solution whose volume is 1.2 L if it contains 0.02 moles of dissolved NaOH M = 0.020/1.2 = 0.01667 = 0.017 M • What is the molarity of an aqueous solution containing 22.0 g of HCl in 1.5 L of solution? Moles = 22.0 g HCl X 1 mol HCl/36.46 g HCL = 0.603 mol M = 0.603mol HCl/1.5L = 0.40mol/L = 0.4M

  31. Calculate Molarity • Calculate the molarity for a solution whose volume is 0.75 L if it contains 0.04 moles of dissolved NaCl • What is the molarity of an aqueous solution containing 40.0 g of glucose (C6H12O6) in 1.5 L of solution? • Calculate the molarity of 1.60 L of a solution containing 1.55 g of dissolved KBr

  32. Calculate Molarity • M = 0.04 mole NaCl = 0.05 mol/L = 0.05M 0.75 L 2. 0.15 M 1.55 g KBr x 1 molKBr/119.002 g KBr ---------------------------------------------- 1.5 L 3. 8.13 x10-3 M

  33. Calculate Molarity • What is the molarity of a bleach solution 9.5 g of NaOCl per liter of bleach? • How much calcium hydroxide, Ca(OH)2, in grams, is needed to produce 1.5 L of a 0.25M solution?

  34. Calculate Molarity • 0.128M • 28 g Ca(OH)2

  35. Dilution Making a new solution from a known amount of a known solution What is changing? Volume Molarity(M) Total number of moles of solute-STAYS THE SAME

  36. Dilution Equation M1V1= M2V2 M1=Molarity of solution 1 V1=Volume of solution 1 M2=Molarity of solution 2 V2=Volume of solution 2

  37. Dilution Problems • You have a stock solution of 2.0 M CaCl2. How much of this solution would you use to make 0.50 L of a 0.300 M CaCl2?

  38. Dilution Problems • M1V1= M2V2 • M1 = 2.00 M CaCl2 • V1 = ? • M2 = 0.300M • V2 = 0.5 L • V1 = M2V2/ M1 • V1 = 0.075 L = 75 mL

  39. Dilution Practice • What volume of a 3.00 M KI stock solution would you use to make 0.300 L of a 1.25 M KI solution? • How many milliliters of a 5.0 M H2SO4 stock solution would you need to prepare 100.0 mL of 0.25M H2SO4 ?

  40. Dilution Practice • 125 mL • 5.0 mL

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